This invention relates to an automatic recording instrument, and more particularly to an apparatus for recording-pen interchange.
In an automatic recording instrument, a movable carriage is provided which can be moved to a desired position in a plane parallel to the surface of the recording paper. A moving pen-holder which is mounted on the carriage, holds a recording-pen. The position of the carriage is computer-controlled to draw a desired trace on the recording-paper by the recording-pen held by the moving pen-holder. The recording instrument has several different recording-pens, and each pen is placed in an assigned store-pen-holder when the pen is not in use. Therefore, there is provided an apparatus for recording-pen interchange to transfer a designated pen between the moving pen-holder and the assigned store-pen-holder.
There have been two main groups in heretofore known apparatus for recording-pen interchange. In the first group, a designated store-pen-holder is moved to a predetermined position where recording-pen interchange is performed. For this purpose, driving means for store-pen-holders and a program for controlling the driving means must be provided in addition to the driving means for the carriage and the control program thereof, resulting in a complex apparatus.
In the second group, store-pen-holders remain fixed and the moving pen-holder is brought to a designated store-pen-holder where the recording-pen interchange is performed. Therefore, the demerits mentioned in the foregoing paragraph are eliminated in the second group. But, all the heretofore known apparatus of the second group have mechanical structure for holding and releasing of a recording-pen, and naturally have following demerits.
(a) Generally, an elastic force is employed to hold a recording-pen, and the pen must be released by opposing this elastic force for recording-pen interchange. This elastic force is sometimes as strong as 250-300 grams, and it is sometimes difficult to exert such a strong force from the driving mechanism of the moving pen-holder.
(b) A complex machanism is required to perform an interconnected chain of motion in which a recording-pen is released from a hold by a pen-holder with the use of a motion of the moving pen-holder, the released pen is transferred from one pen-holder to the other pen-holder, the pen is gripped by the elastic force of the other pen-holder, and then the moving pen-holder recedes from the position. This complex mechanism connected with the reason described in (a) makes the apparatus bulky and expensive.
(c) To perform the interconnected chain of motion described in (b), the accuracy of the relative position between the moving pen-holder and the mated store-pen-holder must be sufficiently high in the position of recording-pen interchange. This high accuracy requirement brings forth a high production cost. When this accurate relative position is not maintained, not only the performance is not smooth, but also there arises a danger of a breakdown of the mechanism.
(d) Since the apparatus has mechanical construction with high accuracy and required a considerable force, the construction must have sufficient strength and becomes heavy and vulnerable to shock and wear.
Therefore, an object of the present invention is to provide an apparatus for recording-pen interchange which has a very simple structure and requires a very small force for the operation.
Another object of the present invention is to provide an apparatus for recording-pen interchange in which a substantial positioning tolerance is allowed. For example, a positioning error of 1-2 mm shall be allowed between the moving pen-holder and the mated store-pen-holder of this invention.
Still another object of the present invention is to provide an apparatus for recording-pen interchange in which all the pen interchange motions are controlled from a computer and there is no necessity to transmit any signal to any pen-holder.
Still another object of the present invention is to provide an apparatus for recording-pen interchange in which the pen interchange motions are very simple and adapted to be controlled by a computer.
Further object of the present invention is to provide an apparatus for recording-pen interchange which holds a recording-pen with sufficient reliability withstanding to shock and wear.